Giant bow shock pairs associated with herbig-haro jets     

Katsuo Ogura 《Astrophysics and Space Science》1995,224(1-2):151-154

Two pairs of giant (linear size 1 pc) bow shock structures have been discovered, each located symmetrically about HH 1/2 and HH 124. Their Herbig-Haro (HH) natures have been confirmed by narrow band CCD imaging on and off [SII] 6717/6731 and/or slit spectroscopy. Multiple bow shocks are known associated with a few HH objects such as HH 34, and are interpreted as evidence for recurrent outflow activity of the exciting sources. The giant bow shocks associated with HH 1/2 or HH 124 provide further, beautiful examples of this phenomenon and, with dynamical ages of nearly 20000 yr in both pairs, extend its timescale by more than an order of magnitude.  相似文献   

Nucleation,growth and stability of CaAl2Si2O8 polymorphs     

Toshiya Abe  Katsuo sukamoto  Ichiro Sunagawa 《Physics and Chemistry of Minerals》1991,17(6):473-484

By means of in situ observation, the nucleation and growth of triclinic, pseudo-orthorhombic and pseudo-hexagonal CaAl₂Si₂O₈ were investigated and their relative stabilities established. Pseudo-hexagonal and pseudo-orthorhombic CaAl₂Si₂O₈ nucleate prior to anorthite and grow in a supercooled anorthite melt before the latter appears. They either dissolve or transform to anorthite once the latter nucleates and starts to grow. Corundum and mullite also nucleate metastably prior to anorthite in this melt. The liquidus temperatures of the four metastably nucleated phases were determined precisely by in situ measurements of the transformation temperatures from a polyhedral to a rounded morphology. On the basis of the supercooling thus determined, the growth rate versus supercooling relations were measured and analysed for the respective phases. The growth rate of the stable phase is one order of magnitude higher than those of any metastable phases. However, the growth rates of the three CaAl₂Si₂O₈ polymorphs normalized by the viscosities are nearly the same.  相似文献   

Mesozoic radiolarians and radiolarian-bearing sequences in the circum-Pacific regions: A report of the symposium-'Radiolarians and Orogenic Belts'     

Atsushi  Matsuoka  Yoshiaki  Aita  Munasri  Koji  Wakita  Gaoping  Shen  Hiroshi  Ujilé  Katsuo  Sashida  Valentina S.  Vishnevskaya  Nkita Y.  Bragin Fabrice  Cordey 《Island Arc》1996,5(2):203-213

Abstract This paper contains extended abstracts of the seven papers presented at the symposium 'Radiolarians and Orogenic Belts' held at the seventh meeting of the International Association of Radiolarian Paleontologists (INTERRAD). Important results of the symposium include the following: (1) Upper Paleozoic and Mesozoic cherts are widely distributed within accretionary complexes in the circum-Pacific orogenic belt. Radiolarian dating reveals that long durations of chert sedimentation in a pelagic environment are recorded on both sides of Pacific-rim accretionary complexes (e.g. New Zealand, Japan, Russian Far East, Canadian Cordillera). (2) Triassic radiolarian faunas from New Zealand and the Omolon Massif, northeast Siberia are similar in composition and are characterized by the absence of typical Tethyan elements. This suggests that radiolarian faunal provincialism may have been established as early as the Triassic. High-latitude radiolarian taxa exhibit a bi-polar distribution pattern. (3) The Lower Triassic interval in chert dominant pelagic sequences is mechanically weaker than other levels and acted as a décollement in accretionary events. This lithologic. contrast in physical property is considered to reflect radiolarian evolution, such as the end-Permian mass extinction.  相似文献   

Crystallization of cosmic dust from highly supersaturated silicate vapor in a rapidly cooled environment     

Hidekazu Kobatake  Katsuo Tsukamoto  Ken Nagashima  Peter Dold 《Icarus》2008,198(1):208-217

Growth conditions and the resultant morphology of cosmic forsterite and enstatite particles condensed from the vapor were investigated experimentally as a function of growth temperature and supersaturation using flash-heating by CO₂ laser irradiation. Forsterite particles grew dominantly, followed by a few pyroxenes. No silica minerals were observed. The forsterite morphology changed systematically depending on the temperature (T) and the vapor supersaturation (σ). As the temperature decreased and the vapor supersaturation increased, the forsterite morphology changed from a bulky type (T=1000-1450 °C, σ<97) to a platy type (T=700-1000 °C, σ=97-161), then to a columnar needle shape (T=500-820 °C, σ=131-230), and finally to a droplet type (T<500 °C, σ>230). Very thin polygonal growth steps, which suggest vapor-solid (VS) growth, were detected on the surface of the faceted bulky and platy forsterite particles. Transmission electron microscopic (TEM) observation showed that the tip of the columnar and needle-shaped forsterite was covered with an amorphous layer. This amorphous coverage illustrates that a liquid phase can be condensed from the vapor, even under the stable conditions where crystalline forsterite is stable. This amorphous layer plays a role in the vapor-liquid-solid (VLS) mechanism of the forsterite particles. The difference in the growth mechanism as a function of vapor supersaturation and temperature can be explained by metastable liquid condensation. The experimentally synthesized coexisting patterns of VS-grown and VLS-grown olivine particles resemble the pattern of matrix olivine or chondrule rims in primitive meteorites. Forsterite can crystallize more easily than either pyroxene or silica minerals, which is consistent with the dominance of forsterite in cometary dust particles, as suggested by its infrared spectrum.  相似文献   

Investigation of the sliding behavior between steel and mortar for seismic applications in structures     

Jason McCormick  Takuya Nagae  Masahiro Ikenaga  Peng‐Cheng Zhang  Mika Katsuo  Masayoshi Nakashima 《地震工程与结构动力学》2009,38(12):1401-1419

The friction developed between a steel base plate and a mortar base contributes shear resistance to the building system during a seismic event. In order to investigate the possible sliding behavior between the base plate and the mortar, a shake table study is undertaken using a large rigid mass supported by steel contact elements which rest on mortar surfaces connected to the shake table. Horizontal input accelerations are considered at various magnitudes and frequencies. The results provide a constant friction coefficient during sliding with an average value of approximately 0.78. A theoretical formulation of the friction behavior is also undertaken. The theoretical equations show that the sliding behavior is dependent on the ratio of the friction force to the input force. The addition of vertical accelerations to the system further complicates the sliding behavior as a result of the varying normal force. This results in a variable friction resistance which is a function of the amplitude, phase, and frequency of the horizontal and vertical input motions. In general, this study showed a consistent and reliable sliding behavior between steel and mortar. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

High-energy observations of solar flares     

Katsuo Tanaka 《Astrophysics and Space Science》1986,118(1-2):101-113

Extensive observations of solar flares made in high energy bands during the maximum of the present solar cycle are discussed with a special reference to the results from HINOTORI, and with attention to the relevant flare models. The hard X-ray (HXR) images from HINOTORI showed mostly coronal emission at 20–25 keV suggesting that the HXR is emitted from multiple coronal loops, consistent with the non-thermal electron beam model in a high density corona. The thermal HXR model seems to be inconsistent with some observations. Three types of flares which have been classified from the Hinotori results are described, along with newly discovered hot thermal component of 30–40 million K which contributes thermal HXR emission. A summary is given for the characteristics of the energy release in an impulsive burst; and an empirical model is described, which explains simultaneous energy releases in multiple loops and successive movements of the release site as suggested from the HXR morphology. The discovery of large blue-shifted hot plasma from the soft X-ray line spectrum leads to some quantitative arguments for the evaporating flare model. An electron-heated flare atmosphere appears to explain various observations consistently.Invited paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

Thermal evolution of flare plasma     

Tetsuya Watanabe  Katsuo Tanaka  Kyo Akita  Nariaki Nitta 《Solar physics》1983,86(1-2):107-113

The evolution of hot thermal plasma in solar flares is analyzed by a single-temperature model applied to continuum emission in the 5 keV < E ? 13 keV spectral range. The general trend that the thermal plasma observed in soft X-rays is heated by the non-thermal electrons that emit as the hard X-ray bursts is confirmed by the observation of an electron temperature increase at the time interval of hard X-ray spikes and a quantitative comparison between thermal energy content and hard X-ray energy input. Non-thermal electrons of 10 keV < E < 30 keV energy may play an important role in pre- and post-burst phases.  相似文献   

Dinosaur footprint assemblage from the Lower Cretaceous Khok Kruat Formation,Khorat Group,northeastern Thailand     

Shohei Kozu  Apsorn Sardsud  Doungrutai Saesaengseerung  Cherdchan Pothichaiya  Sachiko Agematsu  Katsuo Sashida 《地学前缘(英文版)》2017,8(6):1479-1493

The Khok Kruat Formation is the upper part of the Khorat Group, which consists of upper Lower Cretaceous non-marine sedimentary rocks in northeastern Thailand. Many dinosaur footprints have been known from the upper Lower Cretaceous (Aptian–Albian) Khok Kruat Formation at the Huai Dam Chum (Tha Uthen) site, northeastern Thailand. Approximately 600 tracks occur in thin mudstone layer of the northern part of the outcrop at the Huai Dam Chum track site. Two types of footprints, small-sized theropod and crocodylomorph are imprinted with mud cracks and ripple marks on the thin mud layer. Most of footprints are referred to cf. Asianopodus, and are imprinted by small-sized theropoda, probably ornithomimosauria. Theropod tracks are mainly separated into two groups, Group A and Group B. From ichnological viewpoints, the small-sized theropod track assemblage indicates the herd behaviour and its idiosyncratic group composition. In particular, the histogram of size-frequency measurements of Group A shows the anomalous bimodal distribution. We consider that there are two hypotheses; the first one is due to the male-female difference, and the second is a result of the different growing stage.  相似文献   

Measurement and analysis of magnetic field variation during a class 2b flare     

Katsuo Tanaka 《Solar physics》1978,58(1):149-163

We report a digital analysis of high-time-resolution videomagnetograms taken during a class 2b flare that occurred at 60° east. The data were obtained at the Big Bear Observatory and calibrated by a Mt. Wilson magnetogram. Changes of weak magnetic fields (less than 100 G) with an amplitude from 30 to 100% have been detected over 55% of the optical flare region, apparently taking place at the initial phase of the flare. Statistical considerations suggest a real flare association with most of these changes.H observations show that large changes took place over the footpoints of heavily inclined structures like penumbral fibrils, while smaller changes took place over the plage region. An apparent polarity reversal was found at the feet of erupted fibrils.Based on force-free field calculations these changes can be reasonably explained as a transformation of the current-carrying fields to potential fields which produced large changes in the field line inclination and rotation.Visiting Associate, Summer 1977.  相似文献   

The Tiger Sulfide Chimney,Yonaguni Knoll IV Hydrothermal Field,Southern Okinawa Trough,Japan: The First Reported Occurrence of Pt–Cu–Fe‐Bearing Bismuthinite and Sn‐Bearing Chalcopyrite in an Active Seafloor Hydrothermal System     

Kaul Gena  Hitoshi Chiba  Katsuo Kase  Kazuo Nakashima  Daizo Ishiyama 《Resource Geology》2013,63(4):360-370

A sulfide chimney ore sampled from the flank of the active Tiger vent area in the Yonaguni Knoll IV hydrothermal field, south Okinawa trough, consists of anhydrite, pyrite, sphalerite, galena, chalcopyrite and bismuthinite. Electron microprobe analysis indicates that the chalcopyrite contains up to 2.4 wt% Sn, whereas bismuthinite contains up to 1.7 wt% Pt, 0.8 wt% Cu and 0.5 wt% Fe. The Sn‐rich chalcopyrite and Pt–Cu–Fe‐bearing bismuthinite are the first reported occurrence of such minerals in an active submarine hydrothermal system. The results confirm that Sn enters the chalcopyrite as a solid solution towards stannite by the coupled substitution of Sn⁴⁺Fe²⁺ for Fe³⁺Fe³⁺, whereas Pt, Cu and Fe enter the bismuthinite structure as a solid solution during rapid nucleation. The fluid inclusions homogenization temperatures in anhydrite (220–310°C) and measured end‐member temperature of the vent fluids on‐site (325°C) indicate that Sn‐bearing chalcopyrite and Pt–Cu–Fe‐bearing bismuthinite express the original composition of the minerals that precipitated as metastable phases at a temperature above 300°C. The result observed in this study implies that sulfides in ancient volcanogenic massive sulfide deposits have similar trace element distribution during nucleation but it is remobilised during diagenesis, metamorphism or supergene enrichment processes.  相似文献